Cisco IOS Software has several built-in security tools that can be used as part of a good overall security strategy which are covered on the CCNA exam. Probably, the most basic of those security tools are access control lists (ACL) or access lists. Access lists enable us to identify interesting traffic by providing the basic capability to match packets based on a number of criteria. The interesting traffic can then be subjected to various special operations depending upon the specific application. This chapter reviews different types of ACLs, that are available and displays examples of how each of them would be configured in operation. We also introduce Cisco Configuration Professional and how to use it to apply ACLs toward the end of the chapter.